A single clunking noise from the rear after each time the car comes to a stop

I started to notice that my 2017 Prius Prime Plus makes a single clunking (knocking) noise from the rear of the car each time the car comes to a stop. In the past I only noticed it once a while and attributed it to me braking too hard. But recently, I noticed that it occurs every time when I brake and the car comes to a stop (except in the most gentle rolling/gliding to a stop). As the car brakes, inevitably the front end dips and the rear raise a bit due to the momentum. Just as the car comes to a full stop, a single clunking noise can be heard when the rear settles down. It could be repeated even in parking lot: just taking the foot off the brake and let the car move by itself and then apply the brake firmly, the front will dip enough to raise the rear. When the rear settles down, the noise can be heard.

I only drive the car occasionally (10% of the time) while my wife is the primary driver. Now I am aware of it, I notice it all the time. But my wife said the noise was there from day 1 when we had the car brand new (1 year, 8k miles ago). Does this happen with everyone's Prime?

I have seen this post Prius "clunk" when coming to a complete stop with moderate braking | PriusChat. My car's symptom seems very similar to it. Just wonder if this is something I should bring the car to service to check out.

 

I wasn’t asking about noise heard when the car gathering speed. I was asking the noise just AS the car comes to a complete stop and the rear end settles down.

 

Thanks for the suggestion to check the trunk/back seat for loose items. I searched all over and did not find anything rolling/flapping around.

There is a T-SB-0144-16 on 2016 Prius "Some 2016 model year Prius vehicles may exhibit a clicking noise from the support nuts on the rear shocks. " The assembling process was supposed to have been improved to prevent the problem on car manufactured later. I am not sure if that TSB (which was for 2016 Prius, not Prius Prime) applies to 2017 Prius Prime.

I recorded a 10 second video (posted on Google Photo https://photos.app.goo.gl/zhcbSyQiATsagJGB6) with sound to show the speed the car was going and the braking. One could hear the noise at the end.

I made an appointment to bring the car into the dealership to have it checked out.

 

I did not get the same noise when accelerating hard.

I checked and the lug nut wrench and jack are secured.

Hopefully the recording is helpful for explaining to the service department tomorrow.

 

Oh, the back seat bottom seems stable. I could not get any movement by pressing/seating on various part of the back seat.

 

I took the car to the dealership today. They had one of their mechanics to test drive with me. He had no trouble to reproduce the problem.
It was fixed under warranty and seems to be fine so far.
Here is what was included in the invoice for the service.

CUST STATES CLUNK NOISE FROM REAR WHEN COMING TO A STOP
ADVISE
Cause:
Correction: CONMFIRM CUSTOMER COMPLAINT CLUNKING NOISE FROM THE REAR CHECK
REMOVE REAR TIRES TO CHKECK REAR SHOCKS FOUND SHOCKS SECURE PROPERLY TEST
DROVE VEHICLE NOISE STILL PRESENT . CHECK ALL SUSPENTION NUTS AND BOLTS FOUND SOME
REAR SUSPENSION NUTS AND BOLTS A LITTLE LOOSE TORQUE AND SECURE PROPERLY TEST
DROVE VEHICLE FOR NOISE STILL THERE REMOVE TIRES DEGALZED ROTORS SAND PADS AND
LUBRICATE GUIDE PINS AND FIT KIT FOR PADS APPLY SPECIAL BRAKE GREASE TO SHIM KIT AND
FIT KIT SECURE TIRES ROAD TEST VEHICLE NOISE IS NOT THERE ANYMORE

 

Thanks for the analysis. I am not familiar with how the various brake components interact with each other. Any good site that has diagram or animations that shows how it works?

 

Found this video

. It helps to get a better idea.